Blade assembly for a fluid flow machine

ABSTRACT

In a bladed rotor for a gas turbine engine the shrouds or platforms of the blades each have a face which cooperates with a corresponding face on the next adjacent blade to form a radially tapering groove whose width decreases as the radial distance from the rotor axis increases, and a sealing member such as a wire is mounted in the groove to seal between the adjacent platforms or shrouds.

United States Patent Longley et a1.

1 1 Nov. 11, 1975 BLADE ASSEMBLY FOR A FLUID FLOW 2.912.223 11/1959111111 416/221 MACHINE 3.112.915 12/1963 Morris 416/220 3.266.770 8/1966Harlow 416/220 1 Inventors: Peter J g y, Hllton; Anthony 3.709.6311/1973 Karstensen 416/220 x George Gale. Wollaton, both of 3.752.5988/1973 Bowers et a1. 416/220 UX England 3.834.831 9/1974 Mitchell416/193 X [73] Assignee: Rolls-Royce (1971) Limited,

London. England Prmmry E.\anuner-E verette A. Powell, Jr. Attorney,Agent, or F1/'m-Cushman, Darby & [22] Filed: June 3, 1974 C h [21] Appl.No.: 475,916

[57] ABSTRACT 1 1 Foreign Application Priority Data In a bladed rotorfor a gas turbine engine the shrouds June 26. 1973 United Kingdom30252/73 or platforms of the blades each have a face which c0- operateswith a corresponding face on the next adja- [52] US. Cl 416/219; 416/193cent blade to form a radially tapering groove whose [51] Int. Cl. F01D5/18; FOlD 5/24 width decreases as the radial distance from the rotor[58] Field of Search 416/191, 193, 219, 221 axis increases. and asealing member such as a wire is mounted in the groove to seal betweenthe adjacent [56] References Cited platforms or shrouds.

UNITED STATES PATENTS 7 Claims, 6 Drawing Figures 2.445.154 7/1948 Reed416/221 lfl/ Patent N'ov.11,1975 Sheet1of3 3,918,842

US. Patent Nov. 11, 1975 Sheet 2 of3 3,918,842

Nov. 11, 1975 Sheet3of3 3,918,842

US. Patent BLADE ASSEMBLY FOR A FLUID FLOW MACHINE This inventionconcerns a bladed rotor for a gas turbine engine.

In the bladed rotors of gas turbine engines, it is normally necessary toprovide sealing means between the parts of adjacent blades which formpart of theflow annulus, i.e., between the root platforms and/or betweenthe shrouds.

In the past there have been many systems available for providing theseseals, however, most of them have suffered from a similar defect in thatwhilst the seals may be extremely efficient while the rotor isstationary, when the rotor is running at a comparatively high rotationalspeed the centrifugal force acting upon it tends to make it expand andtherefore make the seals less effective. Other difficulties areencountered with the sealing of a turbine rotor due to expansion of theturbine components caused by large change in temperature at which theturbine operates.

It has been found that by use of an embodiment of erates with acorresponding face on the next adjacent blade to form a radiallytapering groove whose width decreases as the distance from the rotoraxis increases in which a sealing member is mounted so as to sealbetween the adjacent platforms or shrouds.

Preferably there is at least one projection from said face or facesadapted to prevent said sealing member falling radially inward todisengage from the groove.

The groove may be formed between a radial surface on one face and aninclined surface on the corresponding face, or between an inclinedsurface on one face and an oppositely inclined surface on thecorresponding face.

In a preferred embodiment the sealing member comprises a wire which iscurved longitudinally to match the curve of said tapered groove.

The invention will now be particularly described merely by way ofexample with reference to the accompanying drawings in which:

FIG. 1 shows a diagrammatic view of a gas turbine engine showing anembodiment of the present invention,

FIG. 2 shows an enlarged pictorial view of the embodiment shown at FIG.1,

FIG. 3 shows a section taken between two respective blades shown at FIG.2,

FIG. 4 shows an end elevation of two adjacent blade roots taken indirection of arrow 4 at FIG. 3,

FIG. 5 shows an enlarged pictorial view of the sealing member, and IFIG. 6 is a view similar to FIG. 2 but of a second embodiment of theinvention.

Referring to FIG. 1 a gas turbine engine shown generally at 10 comprisesan intake 12, compressor section 13, combustion section 14 and turbinesection 15 terminating in exhaust nozzle 16. A brokenaway portion of thecasing round the turbine section 15 shows diagrammatically the turbinerotor in accordance with the invention. I

FIG. 2 is an enlarged pictorial view of the broken away section shown atFIG. 1 and shows individual aerofoil shaped turbine blade members a,20b, 20c and 20d terminating in blade root portions 21a, 21b, 21c and21d only three of which are wholly or partially exposed in the drawings,the blade roots in turn are secured in the rotor disc (not shown) bymeans of fir tree root members. The outer tips of the blades 20a, b, c,d, etc. are in turn bounded by a shroud portion 22 which it will beappreciated may also be provided with a similar sealing system as thatshown at the blade roots.

Referring to the sealing arrangement shown generally at 24 it will beappreciated that a slight clearance must be allowed at the abuttingsurfaces 25 and 26 provided on the blade root portions for manufacturingtolerance, and it is therefore necessary to provide a seal to preventany through flow of air or gas through this gap.

It will be seen that the surface 25 is provided with a recessed portion25', the recess terminating in an inclined arcuate surface 27 againstwhich the arcuate wire sealing member 28 rests. The inclined surface 27and flat surface 26 together form a tapered groove whose width decreasesas the radial distance from the rotor axis increases, and the wire 28 isof the same length as the root portion of the blade. This constructioncan also be seen at FIG. 4. The sealing members 28 are prevented frommoving radially inwardly by means of a projecting portion 29 beingprovided upon the substantially flat surface 26, the projection 29 beingspaced radially inward of that part of the flat surface 26 whichcorresponds with the inclined surface 27.

The sealing members and blades are prevented from moving axially fromthe disc by means of lock plates 30 and 31 shown in more detail at FIG.3.

FIG. 6 shows a further embodiment of the invention, in this case thesealing member 28 is arranged to nestle in the tapered arcuate grooveformed between two inclined arcuate step portions 32 provided upon theradially outermost surfaces of two recessed portions one of which isprovided on each side of the blade root portion; again cooperatingprojections 33 radially inward of the surfaces 32 prevent the member 28falling radially inwardly.

It will be readily understood that during operation of the turbine thecentrifugal load imposed upon the sealing members 28 tend to force themradially outwards such that they are forced into the tapered section 27of the recessed portion 25' (shown at FIG. 2) or between the two taperedportions 32 (shown at FIG. 6) thus providing an efficient sealingarrangement. The material of the wire will be chosen to have sufficientmalleability to enable it to bed into the tapered groove. It will alsobe understood that the arcuate sealing members 28 also help damp outvibration occurring the blades, and by choosing seals of a particularsize and weight, desired damping characteristics could be obtained.

Since the sealing members 28 are interposed between the platforms, theyprevent these platforms fretting against one another, and their positionat the inner end of the aerofoil enables them to provide damping of thisarea; clearly the faster the rotor rotates, the more centrifugal loadacts on the sealing members and the greater will be the damping. It willalso be understood that expansion or contraction occurring in theturbine may be accommodated by the above mentioned sealing arrangements.

It will also be appreciated that by producing seal members 28 in arcuateform the curved shape gives angular location to enable the ends of theseal member to be shaped by machining to conform with the surface of theblade front and rear faces 21a and 21b etc. The arcuate shape alsoprevents twisting of the seal member 28 and ensures friction damping.

It will be appreciated that whilst an embodiment of this invention hasbeen described in connection with a turbine sealing device the inventionis in no way restricted to such a device and could equally well be usedfor the sealing of a compressor rotor or similar device.

We claim:

1. A bladed rotor assembly for a gas turbine engine comprising a rotorand a plurality of angularly spaced apart aerofoil blades supported fromthe rotor, each blade having a platform member, said platform memberhaving a face which cooperates with a corresponding face on the nextadjacent blade to form a radially tapering groove whose width decreasesas its distance from the rotor axis increases, said radially taperinggroove being curved longitudinally relative said rotor assembly, and asealing member mounted in the tapered and longitudinally curved grooveso as to seal between the adjacent platforms, said sealing membercomprising a wire curved longitudinally relative said rotor assembly andbeing substantially complementary to the longitudinal curve of saidgroove.

2. A bladed rotor assembly as claimed in claim 1 and in which there isat least one projection from one said face adapted to prevent saidsealing member falling radially inward to disengage from said groove.

3. A bladed rotor assembly as claimed in claim 1 and in which there is aradially extending surface on one said face and an inclined surface onthe cooperating face between which surfaces is formed said groove.

4. A bladed rotor assembly as claimed in claim 1 and in which there isan inclined surface on one said face and an oppositely inclined surfaceon the cooperating face between which surfaces is fonned said groove.

5. A bladed rotor assembly as claimed in claim 1 and comprising lockplates which engage between said rotor and said blades to limit axialmovement of the blades and sealing members with respect to the rotor.

6. A bladed rotor assembly as claimed in claim 1 and in which saidplatforms comprise the root platforms of the blades.

7. A bladed rotor assembly as claimed in claim 1 and in which saidplatforms comprise the shroud platforms of the blades.

1. A bladed rotor assembly for a gas turbine engine comprising a rotorand a plurality of angularly spaced apart aerofoil blades supported fromthe rotor, each blade having a platform member, said platform memberhaving a face which cooperates with a corresponding face on the nextadjacent blade to form a radially tapering groove whose width decreasesas its distance from the rotor axis increases, said radially taperinggroove being curved longitudinally relative said rotor assembly, and asealing member mounted in the tapered and longitudinally curved grooveso as to seal between the adjacent platforms, said sealing membercomprising a wire curved longitudinally relative said rotor assembly andbeing substantially complementary to the longitudinal curve of saidgroove.
 2. A bladed rotor assembly as claimed in claim 1 and in whichthere is at least one projection from one said face adapted to preventsaid sealing member falling radially inward to disengage from saidgroove.
 3. A bladed rotor assembly as claimed in claim 1 and in whichthere is a radially extending surface on one said face and an inclinedsurface on the cooperating face between which surfaces is formed saidgroove.
 4. A bladed rotor assembly as claimed in claim 1 and in whichthere is an inclined surface on one said face and an oppositely inclinedsurface on the cooperating face between which surfaces is formed saidgroove.
 5. A bladed rotor assembly as claimed in claim 1 and comprisinglock plates which engage between said rotor and said blades to limitaxial movement of the blades and sealing members with respect to therotor.
 6. A bladed rotor assembly as claimed in claim 1 and in whichsaid platforms comprise the root platforms of the blades.
 7. A bladedrotor assembly as claimed in claim 1 and in which said platformscomprise the shroud platforms of the blades.